The present invention relates to a process for making a wet-layed metal fiber nonwoven sheet. In particular, the present invention relates to such a process which employs a fibrillated material in the preparation of the metal fiber sheet.
Papers comprised primarily of metal fibers have been desired by the industry for many years. Various methods have been developed for the preparation of metal fiber sheets. The manufacture of metal fiber nonwoven fabric-like paper structures on papermaking equipment has also been actively pursued due to its commercial attractiveness. Interest in such techniques is described, for example, in the chapter on metal fibers by Hanns F. Arledter in Synthetic Fibers in Papermaking, Editor O. Balestra, chapter 6, pages 118-184. See also U.S. Pat. No. 2,971,877.
The problem in making metal fiber sheets using conventional papermaking techniques is that the metal fibers tend to clump together. Before paper can be made, it is necessary to open fiber bundles to achieve individual fibers and to disperse the fibers uniformly in a fluid. With most wood pulps, the opening is not usually a difficult task. The pulp or source of fibers is placed in water and the mixture is sheared until the bundles open.
With metal fibers, both the opening of the bundles and the dispersion of the fibers in order to keep the fibers separated are difficult. Normal types of mixing or shearing devices can easily damage metal fibers. When metal fibers are bent, they will remain bent and eventually will interact to form balls of tangled fibers. Paper made from fibers in this form is unacceptable.
It would be of great advantage to the industry, therefore, if a process for making a metal fiber sheet using conventional papermaking techniques, i.e., a wet-laying technique, can be used. Such a process should offer efficiency and commercial viability in terms of cost.
Accordingly, it is an object of the present invention to provide a process for making a wet-layed metal fiber nonwoven sheet which is efficient and effective.
Still another object of the present invention is to provide a process for making a metal fiber nonwoven sheet using a fibrillated material.
These and other objects of the present invention will become apparent upon a review of the following specification, figure of the drawing and claims appended thereto.
In accordance with the foregoing objectives, provided by the present invention is a process for making a wet-layed metal fiber nonwoven sheet. The process comprises dispersing a mixture of metal fibers, wood pulp and a fibrillated material into an aqueous dispensing fluid. The amount of metal fibers dispersed generally ranges from 60 to 80 weight percent, based on the weight of solids, with the amount of wood pulp ranging from 15 to 30 weight percent and the amount of fibrillated material ranging from about 5 to 15 weight percent. The dispersed mixture in the aqueous dispensing fluid is then applied to a screen, with the aqueous dispensing fluid being removed to thereby form a metal fiber sheet.
For purposes of the present invention, the fibrillated material is defined as comprising high surface area polymer particles achieved by mechanical or biological or chemical means. Such fibrillated materials can comprise a biologically generated material such as Cellulon, or a fibrid.
Among other factors, the present invention is at least partly based upon the recognition that by using the combination of the metal fibers, wood pulp and fibrillated material, within the designated amounts, a mixture within the dispensing fluid can be created which permits the manufacture of a metal fiber sheet quite easily by conventional papermaking techniques. Upon subsequent sintering of the sheet, the organics can be burned off to provide a metal fiber sheet which comprises at least 99% by weight metal fiber.